Do SPDT On-Off switches conduct electricity...

[booshi]

...through the part of the switch that you flip on and off?  I recently installed some circuit bends into my old synth and before I go plugging this in I want to make sure that it's safe.  I already wired the switches but I haven't mounted them yet, I'm doing that soon.  Just in case it matters they are Mountain Switches from Mouser.  Thanks.

[petemoore]

Not at least that I've noticed...
 Put the DMM all over it and see...

[Peter Snowberg]

If you have any connection from the switching terminals to the switch body, you have a bad switch. Those should never be connected.

Even if there were a short, I'm guessing your synth is all low voltage so it wouldn't matter much anyway. Bend away!

Take care,
-Peter

[booshi]

It's a 9V casio from the 80's.  Gonna go mount the switches now and fire it up!